Apparatus and system for preventing backside peeling defects on semiconductor wafers

ABSTRACT

A apparatus includes a susceptor and a non-reactive gas source. The susceptor has through holes and a wafer support surface. Each through hole includes a lift pin and a lift pin head. The lift pin has a vertical degree of motion in the through hole to lift up or place a wafer on the susceptor. The lift pin head has at least one flow channel structure running from its first surface at least partially exposed to a bottom side of the susceptor through its second surface exposed to a top side of the susceptor wherein the lift pin. The non-reactive gas source is configured to flow a gas to a backside of the wafer through the flow channel structure through the bottom side of the susceptor.

RELATED APPLICATIONS

This is a divisional application of U.S. patent application Ser. No.13/929,297 filed on Jun. 27, 2013, now U.S. Pat. No. 10,163,676 issuedon Dec. 25, 2018, which is incorporated herein by reference in itsentirety.

BACKGROUND

In semiconductor manufacturing, multiple layers (such as a SiN layer, ahigh-K layer, a poly layer, etc.) are deposited on the front side of awafer, in which an adhesion layer (such as SiN) plays an important rolefor adhering the other layers to the wafer. During deposition of thelayers, the layers are unintentionally deposited on the backside of thewafer with little or no adhesion layer. After the deposition of thelayers, the wafer still needs to undergo several subsequent processes,in which some processes may cause a high stress difference between twoadjacent layers, and some processes with high thermal budgets may inducelarge thermal stress in the layers. Such high stress difference andthermal stress may result in backside peeling defects on the wafer,especially on the region of the backside of the wafer on which little orno adhesion layer is formed. The more the layers are deposited on thebackside of the wafer, the higher the peeling defect failure rate willbe. Therefore, the backside peeling defects of the wafer can be avoidedby preventing the layers from being deposited on the backside of thewafer.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present embodiments, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1A is a schematic diagram showing a process chamber with asusceptor for various embodiments;

FIG. 1B is a schematic diagram showing a non-reactive gas flow patternon a wafer support surface of the susceptor depicted in FIG. 1A inaccordance with some embodiments;

FIG. 2A is a schematic explosive view of an exemplary susceptor depictedin FIG. 1A;

FIG. 2B is a schematic cross-sectional view of the susceptor with astraight through hole in accordance with some embodiments;

FIG. 2C is a schematic cross-sectional view of the susceptor with a stepthrough hole in accordance with certain embodiments;

FIG. 3A-FIG. 3D are schematic diagrams showing exemplary types of liftpin heads;

FIG. 4A is an inspection result of film deposition on the backside of awafer when conventional lift pin heads are used;

FIG. 4B is an inspection result of film deposition on the backside of awafer when lift pin heads with flow channel structures shown in FIG. 3Aare used;

FIG. 5 is a defect trend chart showing a backside peeling defect trendwhen lift pin heads with flow channel structures shown in FIG. 3A areused; and

FIG. 6 is a schematic diagram showing a multi-chamber processing systemin accordance with various embodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

It is understood that the following disclosure provides many differentembodiments or examples for implementing different features of variousembodiments. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. The presentdisclosure may repeat reference numerals and/or letters in the variousexamples. This repetition is for the purpose of simplicity and clarityand does not in itself dictate a relationship between the variousembodiments and/or configurations discussed.

Terms used herein are only used to describe the specific embodiments,which are not used to limit the claims appended herewith. For example,unless limited otherwise, the term “one” or “the” of the single form mayalso represent the plural form. The terms such as “first” and “second”are used for describing various devices, areas and layers, etc., thoughsuch terms are only used for distinguishing one device, one area or onelayer from another device, another area or another layer. Therefore, thefirst area can also be referred to as the second area without departingfrom the spirit of the claimed subject matter, and the others arededuced by analogy. Moreover, space orientation terms such as “under”,“on”, “up”, etc. are used to describe a relationship between a device ora characteristic and another device or another characteristic in thedrawing. It should be noted that the space orientation term can coverdifferent orientations of the device besides the orientation of thedevice illustrated in the drawing. For example, if the device in thedrawing is turned over, the device located “under” the other devices orcharacteristics is reoriented to be located “above” the other devices orcharacteristics. Therefore, the space orientation term “under” mayinclude two orientations of “above” and “below”.

The present disclosure is to establish a diffusion barrier between asusceptor and a wafer placed on the susceptor to limit or prevent filmdeposition on the backside of the wafer, such that backside peelingdefects of the wafer in the subsequent processes can be reduced oravoided. The susceptor has through holes and lift pins inserted in thethrough holes. Each lift pin has a lift pin head coupled thereto forraising or lowering the wafer from or on the susceptor. Embodiments ofthe present disclosure are directed to forming grooves and/or holes onthe lift pin heads of the lift pins to intentionally allow a properamount of gas to flow into the backside of the wafer to form thediffusion barrier.

FIG. 1A is a schematic diagram showing a process chamber 200 with asusceptor 110 for various embodiments of the present disclosure. Theprocess chamber 200, such as an ALD (Atomic Layer Deposition) chamber,disclosed herein is used as an example for explanation, and embodimentsof the present disclosure are also applicable to other types ofapparatuses. As shown in FIG. 1A, the process chamber 200 includes thesusceptor 110, an inner chamber 210 and non-reactive gas sources 140.The susceptor 110 has through holes 112 and a wafer support surface (notlabeled) on which a wafer 100 can be placed. In each through hole 112,there are a lift pin 130 and a lift pin head 120 coupled to the lift pin130. The lift pin 130 is operable to have a vertical degree of motion inthe through hole 112 so as to lift up or place the wafer 100 from or onthe susceptor 110 via the lift pin head 120 contacting the wafer 100.The lift pin head 120 has at least one flow channel structure. The flowchannel structure is used for directing non-reactive gas from thenon-reactive gas sources 140 to an area between the susceptor 110 andthe backside of the wafer 100.

In contrast to the reacting gas used for forming deposition films, thegas supplied by the non-reactive gas sources 140 does not participate infilm forming reactions, such as nitrogen, inert gas (for example,argon), etc. The non-reactive gas sources 140 are configured to flow thegas to the bottom side 102 of the susceptor 110, and then the gas flowsto the backside of the wafer 100 through the flow channel structure ofeach lift pin head 120 by diffusion or injection. In some examples, thenon-reactive gas sources 140 are configured to flow the gas to an areaunder the bottom side 102 of the susceptor 110, so as to establish ahigher pressure at the area under the bottom side 102 of the susceptor110 than a pressure in the inner chamber 210 enclosing the wafer supportsurface of the susceptor 110, such that the gas can be diffused into thebackside of the wafer 100 through the flow channel structure of eachlift pin head 120. In certain examples, the non-reactive gas sources 140are configured to inject the gas to the flow channel structure of eachlift pin head 120. The flow rate of the gas should be well controllednot to move or vibrate the wafer. In some embodiments, the pressuredifference between the area under the bottom side of the susceptor 110and the inner chamber 210 is about 0.1-0.2 torr, while the pressure inthe process chamber 200 is about 2-3 torr. While in operation, thenon-reactive gas sources 140 are configured to establish a diffusionbarrier on the backside of the wafer 100, and the reacting gas passingthrough the front side of the wafer 100 to a hot trap is blocked fromentering the backside of the wafer, so as to prevent film deposition onthe backside of the wafer 100, thus reducing or avoiding backsidepeeling defects for the wafer 100 in the subsequent processes.

Referring to FIG. 1A and FIG. 1B, FIG. 1B is a schematic diagram showinga non-reactive gas flow pattern on a wafer support surface of thesusceptor 110 in accordance with some embodiments. To minimize the wafer100 moving or vibrating, the gas establishing the diffusion barrier onthe backside of the wafer 100 is flowed in a symmetric pattern withrespect to a central axis of the susceptor 110.

As shown in FIG. 1B, three lift pin heads 120 are disposed on thesusceptor 110, and each lift pin head has five flow channel structures,as signified by flow arrows 121. The flow channel structures of all ofthe lift pin heads 120 are disposed symmetrically around the centralaxis of the susceptor 110, so as to provide a symmetric flow pattern. Insome embodiments, the number of the flow channel structures of each liftpin head 120 is greater than two, such as three, five or any number thatcan enable the flow channel structures of all of the lift pin headstogether to provide a symmetric flow pattern. On the other hand, thenon-reactive gas flow pattern of the present disclosure is not limitedto a symmetric pattern, and the flow channel structures may be uniformlyor non-uniformly distributed on one lift pin head 120, as long as thewafer vibration and displacement caused by the gas flow from the flowchannel structures can be minimized or none.

As shown in FIG. 2A-FIG. 2C, three lift pin heads 120 and three liftpins 130 are assembled through the through holes 112 of the susceptor110. The flow channel structure of each lift pin head 120 extends from abottom surface 124 (i.e. the first surface) of the lift pin head 120which is at least partially exposed to a bottom side 102 of thesusceptor 110 through a side surface 126 or a top surface 127 (i.e. asecond surface) of the lift pin head 120 which is exposed to a top side104 of the susceptor 110. In other words, embodiments of the presentdisclosure are featured in modifying the lift pin head 120 to form oneor more flow channel structures for directing a gas from thenon-reactive gas sources 140 to an area between the susceptor 110 andthe backside of the wafer 100.

In general, there are two types of through holes 112. As shown in FIG.2B, the through hole is a straight through hole 112 a. In this case, theflow channel structure may be a groove or penetrating hole running fromthe bottom surface 124 of the lift pin head 120 through the side surface126 or the top surface 127 of the lift pin head. As shown in FIG. 2C,the through hole is a step through hole 112 b, in which the lift pinhead 120 may contact a floor 103 of the susceptor 110 to restrict gasflowing through the through hole 112 b. In this case, the groove orpenetrating hole (flow channel structure) of the lift pin head 120 hasto be appropriately formed to prevent the gas from being blocked by thefloor 103 of the susceptor 110. Embodiments of the present disclosuresare mainly to modify the lift pin head 120 to form a flow channelstructure for allowing non-reactive gas to pass through the through hole112 or the lift pin 130 and the flow channel structure to the top side104 of the susceptor 110. It is noted that the applications of theembodiments do not need to change the structures of other components inthe process chamber besides the lift pin head 120 and in some cases, thelift pin 130.

Hereinafter, several types of flow channel structures are provided asexamples for explanation, but embodiments of the present disclosure arenot limited thereto.

FIG. 3A-FIG. 3D are schematic diagrams showing exemplary types of liftpin heads. In some embodiments, the lift pin head 120 has a flangearound its sidewall. However, the lift pin head with no flange is alsoapplicable to embodiments of the present disclosure, i.e. the lift pinhead and the lift pin are of the same outer diameter. As shown in FIG.3A, a flow channel structure of a lift pin head 120 a is a groove 122 acut into a bottom surface 124 a and a small portion of width of a sidesurface 126 a, such that non-reactive gas may flow along a direction A1to a wafer. Since there is little or no room between the susceptor andthe lift pin head 120 a, the non-reactive gas exiting from the groove122 a will be guided by the susceptor towards the top side of thesusceptor.

As shown in FIG. 3B, besides the flow channel structure similar to theone shown in FIG. 3A, a lift pin head 120 b has another two types offlow channel structures. One type of flow channel structure is a groove122 b 1 extending from a bottom surface 124 b of the lift pin head 120 bthrough a side surface 126 b of the lift pin head 120 b to a top surface127 b of the lift pin head 120 b, such that non-reactive gas may flowalong a direction B1 to a wafer. The other type of flow channelstructure is a penetrating hole 122 b 2 running from the correspondinglift pin through the top surface 127 b of the lift pin head 120 b. Inthis case, the corresponding lift pin also has a penetrating holealigned with the penetrating hole 122 b 2, such that non-reactive gasmay flow along a direction B2 to a wafer.

As shown in FIG. 3C, a lift pin head 120 c has two types of flow channelstructures. One type of flow channel structure is a groove 122 c 1 cutinto a bottom surface 124 c and a large portion of width of a sidesurface 126 c, such that non-reactive gas may flow along a direction C1to a wafer. The other type of flow channel structure is a groove 122 c 2extending from the bottom surface 124 c through the side surface 126 cto a top surface 127 c of the lift pin head 120 c, such thatnon-reactive gas may flow along a direction C2 to a wafer.

As shown in FIG. 3D, a flow channel structure of a lift pin head 120 dis a combination of a groove 122 d 1 and a penetrating hole 122 d 2, inwhich the groove 122 d 1 is cut into a side surface 126 d and thepenetrating hole 122 d 2 is formed in the groove 122 d 1. In this case,the corresponding lift pin also has a penetrating hole aligned with thepenetrating hole 122 d 2, such that non-reactive gas may flow along adirection D1 to a wafer.

FIG. 4A is an inspection result of film deposition on the backside of awafer when conventional lift pin heads are used. FIG. 4B is aninspection result of film deposition on the backside of a wafer whenlift pin heads with flow channel structures shown in FIG. 3A are used.The film deposition is indicated by shadow areas shown in the figures.Comparing FIG. 4A and FIG. 4B, the apparatus using the lift pin headswith flow channel structures has much less film deposition on thebackside of a wafer than that using the conventional lift pin heads.Thus, backside peeling defects of the wafer in subsequent processes canbe reduced or avoided.

FIG. 5 is a defect trend chart showing a backside peeling defect trendwhen lift pin heads with flow channel structures shown in FIG. 3A areused. At week t1, the lift pin heads with the flow channel structuresshown in FIG. 3A are used to replace the conventional lift pin heads forproduction. As shown in FIG. 5, the defect counts per wafer are greatlyreduced and meet the defect count goal at and after week t1.

FIG. 6 is a schematic diagram showing a multi-chamber processing system300 in accordance with various embodiments. As shown in FIG. 6, themulti-chamber processing system 300 (such as a cluster tool) includesmultiple process chambers 200 a-200 f, in which each of the processchamber s 200 a-200 f has the lift pin heads with flow channelstructures in accordance with the aforementioned embodiments.

In accordance with some embodiments, the present disclosure discloses anapparatus including a susceptor and a non-reactive gas source. Thesusceptor has through holes and a wafer support surface. Each throughhole includes a lift pin and a lift pin head. The lift pin has avertical degree of motion in the through hole, and is operable to liftup or place a wafer on the susceptor. The lift pin head is disposed onthe lift pin and has at least one flow channel structure running fromits first surface at least partially exposed to a bottom side of thesusceptor through its second surface exposed to a top side of thesusceptor. The non-reactive gas source is configured to flow a gas tothe bottom side of the susceptor.

In accordance with certain embodiments, the present disclosure disclosesa system includes at least one apparatus, and each apparatus includes asusceptor, a non-reactive gas source and an inner chamber. The susceptorhas through holes and a wafer support surface. The inner chamberencloses the wafer support surface of the susceptor. Each through holeincludes a lift pin and a lift pin head. The lift pin has a verticaldegree of motion in the through hole, and is operable to lift up orplace a wafer on the susceptor. The lift pin head is disposed on thelift pin and has at least one flow channel structure running from itsfirst surface at least partially exposed to a bottom side of thesusceptor through its second surface exposed to a top side of thesusceptor wherein the lift pin. The non-reactive gas source isconfigured to flow a gas to the bottom side of the susceptor.

Although the present embodiments and their advantages have beendescribed in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. An apparatus, comprising: a holder having athrough hole and a wafer support surface, wherein the through hole is astep through hole, and a floor of the holder is disposed in the stepthrough hole; a lift pin received in the step through hole and having avertical degree of motion; a lift pin head received in the step throughhole, on the lift pin and having at least one flow channel structurerunning from a first surface of the lift pin head that has a firstportion opposing the floor of the holder and a second portion exposed bythe step through hole adjacent to a bottom side of the holder to asecond surface of the lift pin head, wherein the lift pin is operable tolift up or place a wafer on the holder; and a non-reactive gas sourceconfigured to flow a gas into the step through hole, wherein: the liftpin head has an outer bottom surface, a top surface, and an outersidewall connected between the outer bottom surface and the top surface,one of the at least one flow channel structure is disposed near or onthe outer sidewall and runs from the outer bottom surface that is atleast partially exposed to a bottom side of the holder via the stepthrough hole of the holder through the top surface or the outer sidewallthat is exposed to a top side of the holder, the lift pin is operable tolift up or place the wafer on the holder via the lift pin headcontacting the wafer, an outer diameter of the lift pin head is greaterthan an outer diameter of the lift pin, and the one of the at least oneflow channel structure includes a groove extending from the outer bottomsurface of the lift pin head through a surface of the outer sidewall ofthe lift pin head to the top surface of the lift pin head.
 2. Theapparatus of claim 1, wherein the second surface is a side surface ofthe lift pin head.
 3. The apparatus of claim 1, wherein the secondsurface is a top surface of the lift pin head.
 4. The apparatus of claim1, wherein the at least one flow channel structure is at least onegroove for allowing the gas to pass through.
 5. The apparatus of claim1, wherein the at least one flow channel structure is a groove cut intoa bottom surface of the lift pin head and an outer sidewall of the liftpin head for allowing the gas to pass through.
 6. The apparatus of claim1, further comprising: an inner chamber enclosing the wafer supportsurface of the holder, wherein the holder is a susceptor.
 7. Theapparatus of claim 6, wherein the non-reactive gas source is configuredto establish a higher pressure at an area under the bottom side of theholder than a pressure in the inner chamber.
 8. The apparatus of claim1, wherein the number of the at least one flow channel structure isgreater than two, and the flow channel structures are disposedsymmetrically around a central axis of the holder.
 9. An apparatus,comprising: a holder having a plurality of through holes and a wafersupport surface, wherein each of the through holes is a step throughhole, and each of the plurality of through holes includes: a lift pinhaving a vertical degree of motion; and a lift pin head on the lift pin,the lift pin head having an outer bottom surface, a top surface, anouter sidewall connected between the outer bottom surface and the topsurface, and at least one flow channel structure, one of the at leastone flow channel structure is disposed near or on the outer sidewall andruns from the outer bottom surface that is at least partially exposed toa bottom side of the holder via the through hole of the holder throughthe top surface or the outer sidewall that is exposed to a top side ofthe holder, wherein the lift pin is operable to lift up or place a waferon the holder via the lift pin head contacting the wafer, an outerdiameter of the lift pin head is greater than an outer diameter of thelift pin, and the one of the at least one flow channel structureincludes a groove extending from the outer bottom surface of the liftpin head through a surface of the outer sidewall of the lift pin head tothe top surface of the lift pin head; and a non-reactive gas sourceconfigured to flow a gas to the bottom side of the holder.
 10. A system,comprising: at least one apparatus, each of the least one apparatuscomprising: a holder having a through hole and a wafer support surface,wherein the through hole is a step through hole, a lift pin received inthe step through hole and having a vertical degree of motion; a lift pinhead received in the step through hole, on the lift pin and having atleast one flow channel structure running from a first surface of thelift pin head to a second surface of the lift pin head, wherein the liftpin is operable to lift up or place a wafer on the holder, and the firstsurface of the lift pin head extends laterally beyond an outer sidewallsurface of the lift pin; and a non-reactive gas source configured toflow a gas to a bottom side of the holder; wherein: the lift pin headhas an outer bottom surface, a top surface, and an outer sidewallconnected between the outer bottom surface and the top surface, one ofthe at least one flow channel structure is disposed near or on the outersidewall and runs from the outer bottom surface that is at leastpartially exposed to die bottom side of the holder via the through holeof the holder through the top surface or the outer sidewall that isexposed to a top side of the holder, the lift pin is operable to lift upor place a wafer on the holder via the lift pin head contacting thewafer, an outer diameter of the lift pin head is greater than an outerdiameter of the lift pin, and the one of the at least one flow channelstructure includes a groove extending from the outer bottom surface ofthe lift pin head through a surface of the outer sidewall of the liftpin head to the top surface of the lift pin head.
 11. The system ofclaim 10, wherein the second surface is a side surface or a top surfaceof the lift pin head.
 12. The system of claim 10, wherein the at leastone flow channel structure is at least one groove or penetrating holefor allowing the gas to pass through.
 13. The system of claim 10,wherein the at least one flow channel structure is at least one groovethrough a flange around a sidewall of the lift pin head.
 14. The systemof claim 10, wherein the at least one flow channel structure comprises agroove cut into an outer sidewall of the lift pin head and a hole atleast in the lift pin head, and an opening of the hole is on a sidewallof the groove for allowing the gas to pass through, the groove onlyextending a partial distance along a vertical exterior surface of thelift pin head.
 15. The system of claim 10, further comprising: an innerchamber enclosing the wafer support surface of the holder, wherein theholder is a susceptor.
 16. The system of claim 15, wherein thenon-reactive gas source is configured to establish a higher pressure atan area under the bottom side of the holder than a pressure in the innerchamber.
 17. The system of claim 10, wherein the number of the at leastone flow channel structure is greater than two, and the flow channelstructures of all of the lift pin heads are disposed symmetricallyaround a central axis of the holder.
 18. The apparatus of claim 1,wherein the lift pin head has a sidewall that slants inwardly in adirection from a top to a bottom of the sidewall of the lift pin headand defines the at least one flow channel structure.